The present invention relates to a scanning electron microscope for obtaining an image of a specimen by detecting an information signal which is generated by scanning the specimen with an electron beam and which is characteristic of the specimen.
In a scanning electron microscope, with the aim of moving a position designated on an image to a predetermined position and obtaining an enlarged image corresponding to the designated position, a technique as described in JP-A-54-78075 has been known in which a desired position inside an observation view field is designated by a display pointer and a specimen is moved to the center of the observation view field.
This technique is effective when a position to be observed while being enlarged is within the observation view field. But when the position to be enlarged and observed is outside a view field range or outside a beam scanning permissible region, an enlarged image corresponding to that position cannot be obtained.
In general view field (or observation position) search, it is frequent that a position to be observed which is not only inside an observation view field but also outside a view field range is searched. Accordingly, approximate positioning is first carried out on an image at a magnification effective for view field (or observation position) search and thereafter, the magnification is gradually increased to determine an observation position and an observation magnification. However, the position search method as above lacks the function of marking an observation position and is difficult to achieve when observation is to be again effected at the same position.
An object of the present invention is to provide a scanning electron microscope suitable for facilitating search for an observation position which is outside a view field range.
To accomplish the above object, a scanning electron microscope according to the present invention comprises means for generating an information signal characteristic of a specimen by scanning the specimen with an electron beam, means for detecting the generated information signal, means for obtaining an observation image of the specimen on the basis of the detected information signal, means for storing the obtained observation image as an image which is used to designate observation position, means for reading the stored image for observation position designation, means for displaying the obtained observation image and the read-out image for observation position designation on individual display screen areas, means for designating an observation position on the displayed image for observation position designation, and means for controlling a position of the specimen scanned with the electron beam such that the designated observation position is moved to a predetermined position on the display screen area for the observation image and an observation image corresponding to the designated observation position is displayed on that display screen area.